In recent years, lithium ion secondary batteries with high output and high energy density have drawn attention as a consumer electric device power source such as mobile phones. Further, application of such lithium ion secondary batteries to ships, railroads, automobiles, and the like, which can efficiently use the energy, has been desired.
Further, technologies to store power generated using natural energy such as wind power or sunlight in a lithium ion secondary battery, and to store power from a system have drawn attention for home use and for industrial use. Further, in a smart grid (next-generation transmission network) using an information technology (IT), a technology using a lithium ion secondary battery has drawn attention.
A lithium ion secondary battery is configured to include a positive electrode and a negative electrode that can occlude/discharge lithium ions and a separator in a container. The container is filled with a nonaqueous electrolyte including a lithium salt. Further, the positive electrode is configured to include a metal foil such as an aluminum foil and a positive electrode active material.
As the positive electrode active material, a lithium cobalt oxide (LiCoO2) having a laminar rock salt structure, powder made of an oxide of lithium and a transition metal where a part or all of cobalt atoms of the lithium cobalt oxide is replaced with nickel, manganese, or the like is used, for example. The positive electrode active material is then fixed to the electrode plate by a binder (an adhesive).
As technologies related to electrodes of a lithium ion secondary battery, technologies disclosed in PTL 1 and PTL 2 are known.